Chapter XVII

Former compromises taken up and begun to be fulfilled 301
Estimates of the heat-power of the sun made only from
gravitation hitherto 302
Contraction and condensation of a nebula solid to the
centre. Heat produced from attraction as well as
by gravitation 303
What quantity of heat is produced by a stone falling
upon the earth 304
Showing again that there is a difference between
attraction and gravitation 305
Contraction and condensation of a hollow-sphere nebula,
in the same manner as the solid one 305
Differences of rotation would be greater in a hollow nebula;
because a great deal of the matter would be almost
motionless in a solid sphere 306
In neither case could matter be brought to rest, but only
retarded in motion. Different periods of rotation
accounted for 307
Table of different rates explained 309
Heat produced by gravitation, attraction and churning,
not all constituents of the heat-power of the sun 310
There can be no matter in the sun so dense as water 311
The hollow part of the sun acting as a reservoir of
gases, heat and pressure 312
The behaviour of heat produced in the nebula, and its power 313
How sun-spots are produced 314
Cyclonic motions observed in sun-spots. Why not all in
certain directions, and why only observed in a very few 315
Cyclonic motions in prominences treated of 316
Many other things might be explained, on some of which we
do not dare to venture. Concluding observations 317